He said: “This brave soldier died bringing a better life to the people of Afghanistan.

“We mourn his loss and our thoughts and prayers are with his family, friends and colleagues at this time. His loss has not been in vain.”

British forces had embarked on a massive mission known as ‘Operation Panther’s Claw’ to try and clear insurgents from the Babaji district ahead of the elections.

This latest fatality brings to four the number of soldiers based at Palace Barracks who have been killed since they deployed to Afghanistan in March.

The troops have spent the last five months mentoring soldiers from the Afghan National Army.

Meanwhile, the Government’s already controversial strategy in Afghanistan was thrown into further crisis last night after the Defence Secretary's right-hand man resigned in protest over the treatment of the armed forces.

Eric Joyce, a former major in the Black Watch, announced that he was standing down as the parliamentary private secretary to Bob Ainsworth.

Mr Joyce, who was previously regarded as an ultra-loyalist Labour MP, said he could no longer justify the growing death toll in Afghanistan by arguing that the war would prevent terrorism in Britain.

In a scathing letter to Prime Minister Gordon Brown last night, Mr Joyce wrote: “I do not think the public will accept for much longer that our losses can be justified by simply referring to the risk of greater terrorism on our streets.”